for a 12-24mm f4.2 FF equivalent, it is steep if you compare it to the Sigma 12-24mm f4. It is not that steep if you compare it to the Canon 11-24mm f4. It is not that steep if you look at the amount of glass it contains (805 grams, 20 elements of which 4 aspherical).

But the advantage of APS-C mirrorless gets lost with big and heavy lenses like this and the Fujifilm X-H1.

And both, the Canon as the Sigma will show more details on a bigger sensor - there's nothing in Fuji cosmos coming close to 46-50 MP. UWA are big fun, if the details don't smear together. And also, if high ISO inside rooms don't eat up resolution.